Unusual sensory experiences are reported in 69% of children with autism and these features are thought to have negative consequences on development, adaptive behavior, and family functioning. The purpose of this project is to explain the developmental course, functional impact, and pathogenesis of sensory features with implications for early detection and intervention. The project will study three commonly observed sensory response patterns: hyporesponsive, hyperresponsive, and sensory seeking. The aims are to: 1) determine longitudinal changes in sensory features in children with autism and DD;2) measure how sensory features impact children's adaptive behaviors (daily living, functional communication/social skills, and level of participation in home/community activities), maladaptive behaviors (stereotyped features, social-emotional problems), and family functioning (parental strain);and 3) isolate specific neurocognitive and contextual risk factors that are associated with the observable sensory problems. Four interrelated studies (total n=210) will address these aims. Study 1 (prospective longitudinal design) uses an existing cohort to examine stability of sensory features from the preschool (2-6 yrs) to the school-age (6-12 yrs.) period, and the functional impact of these features on child/ family outcomes. Study 2 employs retrospective video analysis to identify precursors of sensory features in children with autism during infancy (9-18 months), differentiate these from controls, and predict to preschool/school-age developmental outcomes. Study 3 uses a combination of lab measures, personal accounts of parents and verbal children, and in-home behavioral observations to determine the environmental contexts that elicit unusual sensory features and their impact on family functioning in daily life. Study 4 uses electrophysiology (ERP) to test neurocognitive mechanisms (sensory detection, discrimination, involuntary orienting) that are predicted to underlie specific sensory phenotypes. Thus, in a subgroup of children, convergent data from 4 developmental time points (early infancy, later infancy, preschool and school years) will be secured to study change trajectories in sensory features in autism using mixed methods. Our findings may have implications for understanding brain-behavior linkages, early risk markers of unusual sensory features and their developmental course, and novel intervention strategies that may improve child and family functioning.